Apr 26, 2011

Weird Facts

Can you feel the pulse in your wrist? For humans the normal pulse is 70 heartbeats per minute. Elephants have a slower pulse of 27 and for a canary it is 1000!

If all the blood vessels in your body were laid end to end, they would reach about 60,000 miles.
Abraham Lincoln probably had a medical condition called Marfans syndrome. Some of its symptoms are extremely long bones, curved spine, an arm span that is longer than the persons height, eye problems, heart problems and very little fat. It is a rare, inherited condition.
In one day your heart beats 100,000 times.
By the time you are 70 you will have easily drunk over 12,000 gallons of water.
Coughing can cause air to move through your windpipe faster than the speed of sound - over a thousand feet per second!
Germs only cause disease, right? But a common bacterium, E. coli, found in the intestine helps us digest green vegetables and beans (also making gases - pew!). These same bacteria also make vitamin K, which causes blood to clot. If we didn't have these germs we would bleed to death whenever we got a small cut!
It takes more muscles to frown than it does to smile.
That dust on rugs and your furniture is not only dirt. It's mostly made of dead skin cells. Everybody loses millions of skin cells every day which fall on the floor and get kicked up to land on all the surfaces in a room. You could say, "That's me all over."

It takes food seven seconds to go from the mouth to the stomach via the oesophagus. 
A human's small intestine is 6 meters long.
The human body is 75% water.
Your blood takes a very long trip through your body. If you could stretch out all of a human's blood vessels, they would be about 60,000 miles long. That's enough to go around the world twice. 
The width of your armspan stretched out is the length of your whole body. 
The average human dream lasts only 2 to 3 seconds.
The average American over fifty will have spent 5 years waiting in lines.
The farthest you can see with the naked eye is 2.4 million light years away! (140,000,000,000,000,000,000 miles.) That's the distance to the giant Andromeda Galaxy. You can see it easily as a dim, large gray "cloud" almost directly overhead in a clear night sky. 
The average person has at least seven dreams a night.

Your brain is move active and thinks more at night than during the day.
Your brain is 80% water.
85% of the population can curl their tongue into a tube.
Your tongue has 3,000 taste buds.
Your forearm (from inside of elbow to inside of wrist) is the same length as your foot.  
A sneeze travels at over 100 miles per hour. Gesundheit!
Your thigh bone is stronger than concrete.
Your fingernails grow almost four times as fast as your toenails.
You blink your eyes over 10,000,000 a year.
There were about 300 bones in your body when you were born, but by the time you reach adulthood you only have 206.

Apr 24, 2011

Nucleic Acids

If the primary structure of polypeptides determines the conformation of a protein, what determines primary structure? The amino acid sequence of a polypeptide is programmed by a unit of inheritance known as a gene. Genes consist of DNA, which is a polymer belonging to the class of compounds known as nucleic acids.

The Roles of Nucleic Acids
There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) . These are the molecules that enable living organisms to reproduce their complex components from one generation to the next. Unique among molecules, DNA provides directions for its own replication. DNA also directs RNA synthesis and, through RNA, controls protein synthesis. 
The figure above shows DNA → RNA → protein: a diagrammatic overview of information flow in a cell. In a eukaryotic cell, DNA in the nucleus programs protein production in the cytoplasm by dictating the synthesis of messenger RNA (mRNA), which travels to the cytoplasm and binds to ribosomes. As a ribosome (greatly enlarged in this drawing) moves along the mRNA, the genetic message is translated into a polypeptide of specific amino acid sequence.

DNA is the genetic material that organisms inherit from their parents. Each chromosome contains one long DNA molecule, usually consisting of from several hundred to more than a thousand genes. When a cell reproduces itself by dividing, its DNA molecules are copied and passed along from one generation of cells to the next. Encoded in the structure of DNA is the information that programs all the cell’s activities. The DNA, however, is not directly involved in running the operations of the cell, any more than computer software by itself can print a bank statement or read the bar code on a box of cereal. Just as a printer is needed to print out a statement and a scanner is needed to read a bar code, proteins are required to implement genetic programs. The molecular hardware of the cell—the tools for most biological functions—consists of proteins. For example, the oxygen carrier in the blood is the protein haemoglobin, not the DNA that specifies its structure.

How does RNA, the other type of nucleic acid, fit into the flow of genetic information from DNA to proteins? Each gene along the length of a DNA molecule directs the synthesis of a type of RNA called messenger RNA (mRNA). The mRNA molecule then interacts with the cell’s protein–synthesizsng machinery to direct the production of a polypeptide. We can summarise the flow of genetic information as DNA → RNA → protein. The actual sites of protein synthesis are cellular structures called ribosomes. In a eukaryotic cell, ribosomes are located in the cytoplasm, but DNA resides in the nucleus. Messenger RNA conveys the genetic instructions for building proteins from the nucleus to the cytoplasm. Prokaryotic cells lack nuclei, but they still use RNA to send a message from the DNA to the ribosomes and other equipment of the cell that translate the coded information into amino acid sequences.

The Structure of Nucleic Acids
Nucleic acids are macromolecules that exist as polymers called polynucleotides.

The components of nucleic acids. 
(a) A polynucleotide has a regular sugar–phosphate backbone with variable appendages, the four kinds of nitrogenous bases. RNA usually exists in the form of a single polynucleotide, like the one shown here. (
b) A nucleotide monomer is made up of three components: a nitrogenous base, a sugar, and a phosphate group, linked together as shown here. Without the phosphate group, the resulting structure is called a nucleoside.
(c) The components of the nucleoside include a nitrogenous base (either a purine or a pyrimidine) and a pentose sugar (either deoxyribose or ribose).

As indicated by the name, each polynucleotide consists of monomers called nucleotides . A nucleotide is itself composed of three parts: a nitrogenous base, a pentose (five–carbon sugar), and a phosphate group. The portion of this unit without the phosphate group is called a nucleoside.

The DNA double helix and its replication. The DNA molecule is usually double–stranded, with the sugar–phosphate backbone of the antiparallel polynucleotide strands (symbolized here by blue ribbons) on the outside of the helix. Holding the two strands together are pairs of nitrogenous bases attached to each other by hydrogen bonds. As illustrated here with symbolic shapes for the bases, adenine (A) can pair only with thymine (T), and guanine (G) can pair only with cytosine (C). When a cell prepares to divide, the two strands of the double helix separate, and each serves as a template for the precise ordering of nucleotides into new complementary strands (orange). Each DNA strand in this figure is the structural equivalent of the polynucleotide diagrammed below.

DNA double helix

The RNA molecules of cells consist of a single polynucleotide chain like the one shown in  the figure above .In contrast, cellular DNA molecules have two polynucleotides that spiral around an imaginary axis, forming a double helix.

The figure above shows the DNA double helix and its replication. The DNA molecule is usually double–stranded, with the sugar–phosphate backbone of the antiparallel polynucleotide strands (symbolised here by blue ribbons) on the outside of the helix. Holding the two strands together are pairs of nitrogenous bases attached to each other by hydrogen bonds. As illustrated here with symbolic shapes for the bases, adenine (A) can pair only with thymine (T), and guanine (G) can pair only with cytosine (C). When a cell prepares to divide, the two strands of the double helix separate, and each serves as a template for the precise ordering of nucleotides into new complementary strands (orange). Each DNA strand in this figure is the structural equivalent of the polynucleotide in the diagram.

James Watson and Francis Crick, working at Cambridge University, first proposed the double helix as the three–dimensional structure of DNA in 1953. The two sugar–phosphate backbones run in opposite 5′ → 3′ directions from each other, an arrangement referred to as antiparallel, somewhat like a divided highway. The sugar–phosphate backbones are on the outside of the helix, and the nitrogenous bases are paired in the interior of the helix. The two polynucleotides, or strands, as they are called, are held together by hydrogen bonds between the paired bases and by van der Waals interactions between the stacked bases. Most DNA molecules are very long, with thousands or even millions of base pairs connecting the two chains. One long DNA double helix includes many genes, each one a particular segment of the molecule.

Only certain bases in the double helix are compatible with each other. Adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). If we were to read the sequence of bases along one strand as we traveled the length of the double helix, we would know the sequence of bases along the other strand. If a stretch of one strand has the base sequence 5′–AGGTCCG–3′, then the base–pairing rules tell us that the same stretch of the other strand must have the sequence 3′–TCCAGGC–5′. The two strands of the double helix are complementary, each the predictable counterpart of the other. It is this feature of DNA that makes possible the precise copying of genes that is responsible for inheritance. In preparation for cell division, each of the two strands of a DNA molecule serves as a template to order nucleotides into a new complementary strand. The result is two identical copies of the original double–stranded DNA molecule, which are then distributed to the two daughter cells. Thus, the structure of DNA accounts for its function in transmitting genetic information whenever a cell reproduces.

DNA and Proteins as Tape Measures of Evolution
We are accustomed to thinking of shared traits, such as hair and milk production in mammals, as evidence of shared ancestors. Because we now understand that DNA carries heritable information in the form of genes, we can see that genes and their products (proteins) document the hereditary background of an organism. The linear sequences of nucleotides in DNA molecules are passed from parents to offspring; these sequences determine the amino acid sequences of proteins. Siblings have greater similarity in their DNA and proteins than do unrelated individuals of the same species. If the evolutionary view of life is valid, we should be able to extend this concept of “molecular genealogy” to relationships between species: We should expect two species that appear to be closely related based on fossil and anatomical evidence to also share a greater proportion of their DNA and protein sequences than do more distantly related species. In fact, that is the case. For example, if we compare a polypeptide chain of human hemoglobin with the corresponding hemoglobin polypeptide in five other vertebrates, we find the following. In this chain of 146 amino acids, humans and gorillas differ in just 1 amino acid, humans and gibbons differ in 2 amino acids, and humans and rhesus monkeys differ in 8 amino acids. More distantly related species have chains that are less similar. Humans and mice differ in 27 amino acids, and humans and frogs differ in 67 amino acids. Molecular biology has added a new tape measure to the toolkit biologists use to assess evolutionary kinship.

Apr 14, 2011

How to study Biology and succeed

There are no tricks or short-cuts when it comes to succeeding in Biology class. Biology is difficult and there is no substitute for hard work. But what is meant by "hard work"? One component is time spent on task. When we speak of time, we should consider both the quantity of time spent and the quality of time spent.

There is so much material to be understood that a substantial time commitment is required. There is time spent in class, but also time spent preparing for class, reading the assigned pages, upgrading notes, and studying for tests (which might cover as many as 15 chapters). Yet, a student can devote a lot of time to these activities and still do poorly in Biology. This is because the quality of time spent is also an important factor. Many students become discouraged when, though they spend hours and even days studying for tests, they still get unsatisfactory scores. Usually this occurs because what they do when they study is low-quality work.

What are some examples of low-quality work? One example would be reading the textbook just to get the reading assignment out of the way. A student who reads properly, on the other hand, reads with a critical eye, constantly asking him/herself questions like: "If I had to teach this to someone, could I do it?" or "What if this process where screwed up somehow; then how would the results differ?" or "The text's treatment of this topic differs from what I learned in lower secondary (or what I learned in class today); what question could I ask in class that might clear this up?"

Another example of low-quality work is going over and over your class notes. This is an activity that assumes one will be tested in a low-quality fashion, i.e. with test items that require you to do nothing but recall and repeat. This is a false assumption. You will be asked to integrate concepts from different classes, to apply the principles of biology covered in class to situations that were not covered in the class or text, to evaluate new situations in light of the material covered during the test unit. High-quality work entails preparing for such questions. Preparing entails organising the mass of new information in such a way that it helps you understand the way the concepts are related to each other.

A final example of low-quality work is coming to class regularly and just taking notes. Why is this low-quality work? Because many people go on auto-pilot when they takes notes. They switch off their brains and become passive sponges or tape recorders, assuming that later on, they will only need to act like a pair of speakers to play back what was written down. As in other things, your attendance at classes or tuitions  can be either low-quality or high-quality. High-quality attendance entails being critical during the classes, asking questions like: "Why does it work that way?" or "How do we know that? What is the evidence?" "How does that relate to what the teacher said the other day about...?" There is a world of difference between questions such as those listed above and questions like: "Could you repeat that?" or "Could you spell that?" or "Do we have to know this for the test?" The answers to these questions might be important, but asking them does not indicate that critical thinking has been going on, as do the earlier questions.

As you can see, the successful student will necessarily have to work hard. The suggestions above are labour-intensive; they require more mental gymnastics. But just as a gymnast would be foolish to expect to succeed at a complex manoeuver on the first try at an important competition, as foolish would be a student who expected to pass tests requiring higher-order thought processes without first practicing these same processes.

Successful students take pains to carry out some sort of class follow-up activity. For many, this means rewriting their class notes. A lot of students find this activity to be very tedious. An alternative follow-up activity is a strategy known as Concept Mapping. Like rewriting notes, this is an activity that helps you reorganise the information in a way that conforms to your mental "landscape." Better than rewriting your notes, it helps you to discern the patterns and relationships between concepts. Much research supports the effectiveness of this strategy in helping students learn complex material. The process will be detailed in the presentation that accompanies this handout. Below is a summary of the steps in constructing a concept map, followed by guidelines to use in constructing the most helpful maps possible.

Steps in Making A Concept Map
1. Make a list of the concepts from the class.
2. Rank the concepts from most general to most specific.
3. Start each map at the center of the top of the page with the most general concept, which will generally be the chief topic of a particular topic. Below it, place the second-most general concept(s), etc...
4. Circle these two concepts and link them with a solid line.
5. Label the line with a linking phrase.
6. Work your way down the page, adding increasingly specific concepts and looking for crosslinks, which should be drawn with dashed lines.
7. Add details (examples).
8. Do a second version of the map with the goal being to add formerly unnoticed crosslinks and to organise the map so that it flows as logically and as clearly as possible.

Guidelines for the Most Helpful Maps
1. A typical 80-minute class should contain at least 20 (and not more than 45) concepts. Concepts are usually nouns.
2. Label ALL links and crosslinks with linking phrases. Links generally consist of verbs, but other words may be used where appropriate.
3. Circle the concepts, leave examples uncircled.
4. Each concept should only appear once in a given map. Redundancy of concepts usually indicates that you missed an important conceptual relationship.
5. Concept maps should flow down the page only.
6. Concept maps should NOT resemble flow charts or chronologically based outlines of the class. They should not be sentences with some words diagrammed. An important goal is to accurately relate as many concepts as possible using crosslinks. Maps with long strings of concepts or with several isolated and unlinked branches indicate misunderstanding of the goal of concept mapping.

Further Suggestions:
1. Attend ALL classes: This gives you a good idea of what the teacher(s) think most important. It also allows you to learn by hearing and seeing simultaneously -- much more effective than either one of these alone.
2. Make a regular appointment with your teacher to go over questions you have, or test your own understanding by explaining material back to him/her. It is always better not to be an anonymous face in a crowd -- get to know you teachers.
3. Come to class prepared by having outlined the assigned pages ahead of time. This will help you make more sense of the class as you listen to it and this, in turn, will help you to...
4. Engage your brain in the class. Don't allow yourself to become a note-taking automaton. Think! Be critical! Be skeptical! Ask questions! If you are shy, ask questions after class or during office hours.
5. Put proper closure on each class. Within 24 hours of each class -- the sooner the better -- (1) ask yourself what the class was about without using your notes, and (2) write your answer in the form of a concept map. This is the best time to spot points of confusion or discrepancies between text and notes, which you should write down and follow-up on. It is very important to spend time in this fashion if you are serious about succeeding in biology.
6. Pay attention to the figures in your text, especially the summary figures, like Fig. 17.26 in Campbell's Biology, 7th edition. Figures are expensive to produce and publishers try to use them sparingly in order to reinforce main points.
7. Budget your time. There is such a huge amount of material to be mastered that studying cannot be put off into an all-night cram session before tests. This is a time-tested recipe for failure; if not failure of the test itself, then failure to understand biology. Will you have a cumulative final exam? What is your plan for keeping material from the beginning of the semester fresh and in mind? You would be well-advised to have such a plan.
8. Don't be a hermit. Once you have studied a good bit on your own, get together with a few others who are interested in understanding biology in order to bounce questions off each other, compare concept maps, create sample test questions, explain concepts to each other, and to be able to answer your colleagues' questions regarding those same explanations.
9. Don't miss the forest for the trees. Concentrate on the concepts, not on the minutiae. You will not be asked to recall picky details or to memorise tables (like the genetic code). You will be asked to apply broad concepts to solve specific problems.

Good luck.

Apr 8, 2011

Fake Egg

Fake eggs are still going strong in China. Danwei.org published a small report in 2004 and several blogs reported on fake eggs such as The Raw Feed and Chinaview (in 2007 and 2006), but a look at the stories from Chinese language sources show that the problem is still there, if not bigger than before.

The profit margin for fake eggs, estimated at USD$70 per day, is more than enough for the common Chinese to engage in the business and there’s nothing China’s poor won’t do to get ahead. The list of faulty (or deadly) products coming out of China is long and will continue to lengthen for some time to come. It’s simply a matter of economy and history.

A cursory search of Chinese language news sites brought up more than 8,000 hits for “man-made eggs” including numerous news reports, instructional videos and most galling of all, dozens of ads for training manuals for interested entrepreneurs

In order to tell the difference between man-made and natural eggs, the first method is to inspect the shell. Man-made eggshells are particularly shiny and if the egg is opened, the egg white is not as sticky as a natural egg and is easily mixed in with the egg yolk. There may also be a light chemical smell coming from the egg yolk/white, whereas natural eggs have a fresh smell.

Man-made eggshells are made from Calcium Carbonate. The egg whites and egg yolks are made from the following materials: Alginic Acid, Potassium Alum, Gelatin, Calcium Chloride (with water) and artificial colouring. If fake, the yolk will quickly break up when fried

Man-made eggs are manufactured with chemicals, most importantly through the calcification of Alginic Acid. Man-made eggs are basically solidified gel. Most of the ingredients are additives that are regulated under Chinese law. None of these additives have any health benefits; man-made eggs cannot be considered a viable alternative to natural eggs.

Many of the ingredients involved in the manufacture of man-made eggs come in industrial and commercial forms. Considering the extremely low cost price of man-made eggs, it is uncertain what form of these additives the manufacturers are using. Research has shown that long-term consumption of man-made eggs can lead to memory-loss and dementia.

Check out this Health News Sohu story written by a journalist for the Qilu Evening News in Shandong.

In this story, the journalist follows the trail of one of the ads to a man in Shandong who claims to be the “Father of Man-made eggs”. The man, never named, tells how he charges 800RMB (US$120) per student. In his classes, the “Father” teaches how to make the egg-shell (the most important part of the process) as well as the yolk and white. According to the report, the man has taught college graduates as well as peasants and enjoys a comfortable living — safe from the authorities or anyone else — teaching down and out Chinese how to make fake eggs and get rich.